The local leo cold cloud and new limits on a local hot bubble

J. E.G. Peek*, Carl Heiles, Kathryn M.G. Peek, David M. Meyer, J. T. Lauroesch

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

We present a multi-wavelength study of the local Leo cold cloud (LLCC), a very nearby, very cold cloud in the interstellar medium (ISM). Through stellar absorption studies we find that the LLCC is between 11.3 pc and 24.3 pc away, making it the closest known cold neutral medium cloud and well within the boundaries of the local cavity. Observations of the cloud in the 21 cm H I line reveal that the LLCC is very cold, with temperatures ranging from 15 K to 30 K, and is best fit with a model composed of two colliding components. The cloud has associated 100 μm thermal dust emission, pointing to a somewhat low dust-to-gas ratio of 48 ×10-22 MJy sr-1 cm 2. We find that the LLCC is too far away to be generated by the collision among the nearby complex of local interstellar clouds but that the small relative velocities indicate that the LLCC is somehow related to these clouds. We use the LLCC to conduct a shadowing experiment in 1/4 keV X-rays, allowing us to differentiate between different possible origins for the observed soft X-ray background (SXRB). We find that a local hot bubble model alone cannot account for the low-latitude SXRB, but that isotropic emission from solar wind charge exchange (SWCX) does reproduce our data. In a combined local hot bubble and SWCX scenario, we rule out emission from a local hot bubble with an 1/4 keV emissivity greater than 1.1 Snowdens pc-1 at 3σ, four times lower than previous estimates. This result dramatically changes our perspective on our local ISM.

Original languageEnglish (US)
Article number129
JournalAstrophysical Journal
Volume735
Issue number2
DOIs
StatePublished - Jul 10 2011

Keywords

  • Hii regions
  • ISM: clouds
  • dust extinction
  • line: profiles
  • solar neighborhood

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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